MORTGAGE SERVICING RIGHTS AND MSR FINANCING RECEIVABLES - Rollforward of Carrying Value of Investments In MSRs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Mortgage Servicing Rights [Roll Forward]
Beginning balance	$ 4,585,841	$ 5,686,233
Purchases, net	10,949	431,608
Originations	1,331,626	666,414
Purchases, net	63,451	15,341
Realization of cash flows	(1,196,527)	(1,592,281)
Change in valuation inputs and assumptions	680,431	(591,439)
(Gain) loss realized	2,410	647
Caliber acquisition (Note 3)	1,507,524
Ending balance	$ 6,858,803	$ 4,585,841